Art of sintering ores



Patented Dec. 14, 1948 Ul'iED STATES ''Ei FFICE.

ART OF SIN'IERNG 0RES Application April .20, 1945, Serial No. 589,412

3 Claims Our invention relates in general to improvements in the art of sintering ore, and relates more specifically to an improved method of and apparatus for sintering various types of ore with the aid of magnetism or magnetic influence.

The primary object of thepresent invention is to provide various improvements in the art of sintering ore, whereby such treatment may be most economically and efficiently effected without loss of valuable substances.

It is common practice in the art or metallurgy, to snter or fuse finely divided ore particles into larger masses or lumps, after the ore has been concentrated and before the concentrates are charged into the smelters, in order to prevent undesirable ore dust losses. Likewise, it le common practice to sinter or fuse blast furnace fiue through the bed of material until the fuel has been consumed and the ore particles are nodulized. 'Ihe air fiow through the charges resting upon the gratebars is ordinarily produced by suction pressure established beneath the grate, and the sintered ore is subseqnently cleposited from the sintering grate upon a grizzly for eventua] delivery to the smelters.

With these prier sintering methods, it is necessary to space the grate bars apart sufficiently to prevent the fine ore particles irom seing sucked freely through the grate openings, and the finer the ore the closer the bar spacing must be. As the grateopenings are reduced in size, greater suction is required to provide suffibient volume of fresh air, and increased suction means .111-

creased power consumption and c'est; and if the desirable to maintain the grate openings as large as possible in order to reduce the suction efiort to a minimum; and to positively prevent free passage of fine material through these large openings.

We have discovered that these desirable results may be most electively accomplished With the aid oi magnetism; when sintering .either magnetie or non-magnetic ores, by simply properly' magnetizing the individual grate bars "ina manner wherebythe magnetie fields created betweenad jacent bars Will restrain the particles from being sucked out of the bed through the large grate In the case of magnetic ores, theore openings. particlesthemselves may be magnetized-in orde1' may be mixed with magnetic blast furnace fiu dust or other-relatively fine magnetic material which may be pre-magnetized so asto produce a desirable degree of fiocculation and pelletizatidn or the ore in the charges being treated;

It'is therefore a more specific object of 0111 mes entinvention to provide a new and usefuI process of sintering finely divided ore particles withmin imumpower consumption and with least loss of material, by properly magnetizing the bed sup porting grate bars so as to permit free passageof gas while preventing undesirable escape of ore particles through the grate openings.

Another specific object of the invention is to provide an improved method of treatingfinely divided charges of ore and othermaterials pre paratory to sintering the ore, by pre-magnetizing either the ore particles themselves, or finely'dividedparticles of other material mixed with the A further specific object of this invention-i5 to provide an improved grate for effecting most efiicient and economical sintering of ore beds dis posed thereon, and which is readily applicable to" -either batch or continuons ore sintering assem blages;

Still another specific object of our inventionis to provide an improved magnetized ferrous grate bar assemblage especially adapted for the sinter ing of finely divded ore mixed with fueland water to produce a homogeneous mass or mixture WhiCh" is subject to ignition and penetration by combus=.

tion supporting air.

An additional specific object of the present invention is to provide a simple, compact and highl eificient ore sintering machine of the type comprising a series of horizontal parallel ore and fuel supporting grate bars through the separatingv spaces of Whch air is adapted to be drawn by suction from beneath the bar series.

These and other specific objecte andpadvanc. tages of the invention will be apparent. frOm the.

following detailed description.

A .clear conception of the features constitutingg; "Our present improvement, and of the construction and mode of operating machines when carrying on our new method, may be had by reerring to the drawing accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

Fig. 1 is a diagrammatic side elevation of a fragment of an ore sintering assemblage, looking toward the ends of the ore bed supporting grate bars;

Fig. 2 is a similarly diagrammatic top view of the grate bars embodied in the assemblage of Fig. 1;

Fig. 3 is an enlarged transverse vertical section through an adjacent pair of permanently magnetized grate bars, illustrating the magnetic fields normally produced by these bars; and

Fig. 4 is a similarly enlarged transverse vertical section through an adjacent pair of electrically energized magnetic grate bars, aise showing the magnetic fields normally produced thereby.

While our invention has been shown and de scribed herein as being especially adapted for application to an re sintering assemblage et the suction type, it is not our desire or intention t0 unnecessarily limit the scope or utility of the improvement for analogous purposes, and the designations N and S appearing on the drawings indicate positive and negative polarity respectively.

In accordance with our present invention, and as shown in the drawing, we provide a grate for an ore sintering machine or the like, comprising a series of elongated parallel bars 6, 1, which may be either permanently magnetized or magnetized by induction, so as to create fields of magnetic influence between the successive or alternate adjacent bars of the grate. As shown, the bars 6, 1 are preferably so magneti2ed that the upper and lower portions of the successive bars 6, 1 are of opposite polarity, that is, the upper portions of the bars 6 are positively charged and the lower portions thereof are negatively charged, while the upper portions of the intervening bars 1 are negatively charged and the lower portions thereof are positively charged. By thus magnetizing the bars 6, I of the series, relatively strong mag netic fields are created across the upper and lower portions of the spaces 8 separating the adjacent grate bars, and these fields of inagnetic influence extend throughout the entire length of the bars or entirely across the grate.

When permanently magnetized grate bars 6, 1 are utilized as in Figs, l, 2 and 3, it is preferable to form these bars of metal such as Alnico having highly magnetic characteristics. This metal consists of a compound of aluminum, nickel, cobalt and iron, and is susceptible of powerful magnetization for indefinite duration. However, the grate bars need not be permanently magnetized and may in fact be magnetized by inductio n as illustrated in Fig. 4, wherein the bars 6, I are properly magnetized with the aid of electrically energized coils 9, I0 respectiVe1y longitudinally embracing the medial portions of the bars 6, I. These coils 9, Il] may be embedded in recesses Il formed in the bars 6, I, and may be energized in any convenient and well known manner.

When the graine bars 6, 1 have been properly assembled and magnetized they provide a grate for supporting a bed of homogeneous mixture I2 of finely divided 0re, sufficient fuel t0 eiect nodulation of the 0re, and water in sufiicient quantities to hold the solid particles together. This mixture bed 12 may be caused t0 rest upon the grate and may be of any desired depth, and the bed 12 is preferably constantly supplied with combustion supporting fresh air which may be dravvn through the mess and through the grate openings 3 by suction created in the zone beneath the bars 6, i in a well known manner and as indicated by the arrows in Figs. 3 and 4.

If the 0re to be treated is of a magnetic type, it may be found advantageous in order to loosen or flocculate the bed [2, to pre-magnetize the 0re particles before they are subjected to sintering, and this may also be done in any convenient and well known manner. In case the 0re is not inherently magnetic, some degree of fiocculation of the charge may be attained by including in the mixture a suitable quantity of pre-charged magnetic pulverulent material such as blast furnace flue dust or magnetite which is ordinari]y available in metallurgical plants. Such premagnetizing of the charges besides loosening or flocculacing the beds [2 also assists in pelleti2ing the ore prior to sintering and permits freer passage of air and gases therethrough, thus facilitating more rapid and less restrained flow of the gases toward the discharge spaces 8.

While the improved method of sintering 0re in accordance With our present invention should be apparent from the foregoing description, a short rsum of the process will be repeated. Aiter the grate bars have been properly magnetized, constructed and assembled so as to produce relatively Wide and unobstructd intervening spaces 8, and the mixture of 0re, fuel and water has been properly prepared, successive charges or beds I2 of the mixture may be deposited upon the assembled grate, whereupon the fuel should be ignited and suction should be created beneath the grate and bed. The burning fuel in the charges will evaporate the water and nodulize or fuse the fine ore particles, and fresh air will be drawn into the top of the beds while the gases of combustion will be constantly withdrawn through the spaces 8 by suction.

During this sintering performance or operation, the magnetized grate bars will create relatively strong fields of magnetic influence above and below each complementary pair of adjacent bars as -clearly shown in Figs. 3 and 4, and these magnetized zones or fields will cause some of the magnetic particles of the charges t0 assume gap bridging groups or patterns spanning the large spaces 8 at their lower and upper ends. This bridging action places a relatively loose bariier across each and of each space 8, which while permitting relatively iree fiow of gases therethrough, positively prevents ore particles from dropping out of the mass of mixture. When the fuel has been completely consumed, the sintering or nodulization will have been completed, and successive charges may thus be quickly and effectively treated With the aid of minimum suction effort and without losing valuable 0re.

It is a well known fact that permanent magnets when subjected to excessively high temperatures, rapidly lose their magnetism, but that a moderate increase in temperature improves the magnetic properties. It is also a well known fact that the sintering of ores is accomplished at relatively high temperatures which if directly applied to a permanent magnet, might undesirably affect the magnetization. We have found, however, that With our improved method, the extreme sinter ing temperatures do not materially afiect permanently magnetized bars 6, l since these bars are adapted to rapidly radiate the heat into the spaces 8 and into the suction zone, and that the temperatures to which these bars are actual1y subjected during sintering are not suificient to undesirably affect the magnetization thereof. We have also found that by magnetizing the grate bars, the spaces a oan be made considerably larger than is possible without utilizing the present improvements, while stil1 avoiding loss of valuable 0re particles. It is also noteworthy that when the bridges of magnetic material have been produced, they remainin place and provide a cushion for the bed l2, and in cases where the ore has non-magnetic characteristics, the improved resu1ts may be obtained either by applying magnetic pulveruient material to the charges, or by initially placing a layer of magnetic particles near the magnetic bars 50 as to produce the bridgng patterns before the charges are actua1ly applied to the grate. Our invention has in fact proven highly successful in actual use and has established the fact that magnetization of the grate bars W111 permit more rapid and effective sintering at minimum cost and without the 1055 of valuable product. By pre-magnetizing magnetic ores, the charges of material being sintered may also be maintained in loosened and flocculated condition, thereby facilitating the impregnation of the charges with fresh combustion supporting air; and it has been found that when either magnetic or non-magnetic ore is being sintered, there is an intense magnetic zone produced around the bars, and this magnetic action loosens and fiocculates the ore in the vicinity of the grate t0 a depth of several inches or more.

It should be understood that it is not desired to limit this invention to the exact details et construction or to the precise steps of the method, herein shown and described, for various modifications within the scope of the appended claims may occur to persans skilled in the art.

We claim:

1. The method of sintering a static bed of mixed magnetic 0re and fuel particles resting upon a grate having supp0rting bars spaced apart suficientiy t0 normally permit particles of the mixture t0 gravitate freely through the spaces, which comprises, magnetizing and maintaining the bars constantiy magnetized with sufiicient intensity to cause the magnetic particles to loosely bridge each space with bridges sufficiently dense to prevent particles of the mixture from falling through the spaces, and igniting the fuel particles to sinter the mixture and continuing the sintering operation by passing combustion air and gases through the bed and spaces.

2. The method of sintering a static bed of mixed magnetic 0re and fuel particles resting upon a grate having supporting bars spaced apart suificicntly to normally permit particles of the mixture to gravitate freely through the spaces, which comprises, individually magnetizing and maintaining each bar constantiy magnetized with sufficient intensity to cause the magnetic particles to loosely bridge each space with upper and lower bridges suficiently dense to prevent particles of the mixture from falling through the spaces, igniting the fuel particles to sinter the mixture and continuing the sintering operation by admitting combustion air to the bed, and discharging the gases of combustion downwardly through the bridges and spaces.

3. A grate assemblage for sintering a static bed resting thereon and composed of mixed magnetic 0re and fuel particles, which comprises, a series of bed supporting bars separated by elongated structurally unobstructed spaces of su1- cient width t0 norma]ly permit most of the particles of the bed to gravitate iree1y therethrough, said bars being individually constantly magmatized with suficient intensity to cause magnetic particles of the mixture to bridge the upper and 1ower portion of each space with bridges sufficiently dense to support the entire bed above the grate and to prevent any particles of the mixture from falling through said spaces while permitting free flow of gases through the latter.

ROBERT L. MANEGOLD. IRA H. WYNNE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,048,111 Gahl July 21, 1936 2,048,113 Gahl July 21, 1936 OTHER REFEREN CES Electromagnetic Devices, by Herbert C. Roters, 1941, pages 45 and 46. 

